Method of controlling electric motors.



92 (-.LU!U1616K O C UHAFTSWEAWL SlOP C No. 665,321. Patented m. l, muff F. w. GARRETT. METHOD OF CONTROLLING ELECTRIC MOTORS.

(Application Med Mar. 26, 1900.!

(No Model.) 2 Sheets-Sheet I.

WITNESSES: mvmron 551% ATTORNEY.

N0. 665,32l. Patented .Ian. I, l90l. F. W. GARRETT.

METHOD OF CONTROLLING ELECTRIC MOTORS.

(Application mad Mar. 26, 1900.) (No Model.) 2 Sheets-Sheet 2.

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UNITED 7 rams.

FRANK W. GARE-m nor JonNs'rowN, PENNSYLVANIA, ASSIGNOR TO THE LORAIN sTEnLcoMPANY, OF PENNSYLVANIA.

METHOD OF CONTROLLING ELECTRIC MOTORS.

SPECIFICATION forming part of Letters Patent No. 665,321, dated January 1, 1901.

Original application filed August 24:, 1899, siin lio. 728,379. Divided and this application filed March-26, 1900. Serial No.

10,152. \No model.)

To. all whom it may concern.-

Be it known that I, FRANK W. G RRETT, of J ohnstown, in the county of Oambria and State of Pennsylvania, have invented a new and useful Improvement in Methods of Controlling Electric Motors, of which the-following is a full, clear, and exact description, reference being had to the accompanying drawings',-which form a part of this specification. This invention has relation to a novel method of controlling electric'motors and the mech pism or mechanisms driven thereby, and signed to provide a method of control which is economical in point'of current con- I 5 sumption', none, of the current b'eing'wasted by the interposition of useless resistance, which permits a gradual starting and acceleration of the driven mechanism, and which reduces very largely the wear and tear of the 2o driving-gears, the commutators,brushes,-and

bearings, and also the danger of bursting the armature-bands when running at high speed on downgrades. t

The invention consists in a method of con- 25 trolling a plurality of electric motors by starting them from a position of rest, connected in series with each other'and mechanically disconnected from the parts to be driven thereby, then efiecting a gradual mechanical 3o connection between the motors and the driven parts and then changing the m tors over to parallel relation. F

It also consists in the employment of several steps in addition to the above by means of which the circuit is opened and the motors mechanically disconnected from the driven parts preparatory to connecting them in mul- .ftiple relation, after which the multiple con- I nection is effected and the mechanical con- 40 nection between the motors and the driven mechanism is graduallyrestored.

The invention also consists in certain other novel features and combina'tionsmhereof, all.

as hereinafter described, and pointed out in the appended claims.

The invention is applicable .tostationary motors, as well as to those employed in propelling moving vehicles, and the magnetic clutch embraced by the inventionlmaybeused to advantage in the control of various kinds of machinery.

Referring to the accompanying drawings, Figure l is a View, partly in' section and partly in plan, showing my improved clutch as applied to an electric motor. lar view showing a modified form of clutch. Fig. 3 is a diagrammatic view illustrating the invention applied to the control of two electric motors and showing the clutch and circuit connections. Fig. 4. is a diagrammatic View showing the circuit relations in the several different positions of the switch.

The letter A, Fig. 1, designates a motor frame or casing, A the armature, and a the armature-shaft, turning in bearings in said frame or casing. B is a clutchplate fast to said shaft and formed of magnetic material, either iron or steel. B is a second plate of similar material, loosely mounted on said shaft and carrying a pinion B rigid therewith and meshing into a gear-wheel D, forming part of the driven mechanism.

Formed in the inner face of the plate B is an annular groove b, in which is seated a magnet-coil O, which is composed of a number of independent sections, any desired number of which may be connected in series through the medium of the switch hereinafter described. In'the diagram, Figs. 3 and 4, I have shown this magnet-coil as composed of three sections. E designates brushes which bear upon the rotary clutch-plate B and are electrically connected with contacts of the said switch. One pair of these brushes is provided for each section of the magnet-coil, and each is electrically connected to its corresponding section, as indicated.

1) b are renewable wear-plates, of iron or steel, detachably secured in any suitable manner to the inner faces of the respective clutchplates. The use of these removable plates is advantageous from an economical standpoint; but they are in no way essential to the invention and may be omitted, as shown in Fig. 2. v

In Fig. l I have shown an oil-box O, in which the clutch turns.

The operation of the clutch will be readily latter to attract the movable plate'B" into understood. The coil 0 being energized magnetizes the clutch-plated; audc'auses the contact therewith and effect a driving connection between the armatureshaft and the gear-wheel D. The degree of slippage between the two plates (current strength and lead on the clutch being equal) depends upon the extent to which the coil 0 is energized, being comparatively great when but a single section of said coil is in circuitand m'l when all the coil-sections are energized.

In the modification shown in Fig. 2 instead of rotating the magnet-coil'I inclose same in an extension A of the motor frame or casing and surrounding the two clutch-plates, which are thus brought within the field of the coil and act as a core therefor. The tendency of the lines of force composing said .field to shorten causes the clutch-plates to be attracted into contact with the fixed plate, and thus establish the driving connection between the armature-shaft and the gear-wheel D, as in the construction first described. 13 designates springs interposed .hetweenYthe two clutch-plates and tending'to separate the same.

Referring now to the diagram Fig. 3 the letters A A designate the armatures of a pair of motors, F F the field-coils therefor, and G C the sectional magnet-coils connected in multiple with each other. T designates the connection with one side of the line, and G a ground connection through one ofthe armature-shafts. S is the controlling-switch, which is preferably of the well-known rotary type, having a plurality oficontacts' secured to the periphery of its drum. These contacts are shown as arranged in three groups, all the contacts of each particular group being connected electrically ,with each other, but disc'onncctedelectrically fromthe contacts of the. other groups. In the first group are contacts c to 0 inclusive, in the second group a to c, inclusive, and in the third group contacts and 0 The contacts of the first group control the magnet-coil those of the second group the series con ion of the motors, and-those of the third group the parallel connection thereof. In addition to the contacts above described I provide the controller-drum with a line of short contacts 00, m 00 and sc on the vertical line X, which are engaged, respectively, by the fingers-7, 11, 13', and 14: before reaching the first-indicated or No. 1 positionof the switch. Similar contacts y to 11 inclusive, are-(provided on the vertical line Y-for engagement with fingers 7, 11, 12, 13, let, and 15 just beforepassing to indicated position No. .ei.-. ,,1he position in which these contacts y to 3 are engaged, like the position in which these contacts .22 to m are engaged, is not indicated on the controller. The purpose of these two sets of contacts will hereinafter appearMBt-W aws positionNo. 3 and the line of contacts 1" point of open circuit. FingerNo. is

isla- 1 I connected to the trolley side of the circuit. Fingers S, 9, and 10 connect the different sections of the two magnet-coils in parallel and to the motor-circuit. Fingers 11 and 12 are connected to each other and to field-coils F. Finger 18 is connected to field-coil F and through said coil and armature A to ground. Finger 1 1 is connected to armature A. Finger 15 is connected to ground G Upon the initial movement of the switch fingers 7, 11, 13, and 1 1 engage the contacts w .00 WW, and the path of the current is from trolley T to finger 7, contacts 00' m finger 11, field F, armature A, finger 14, contacts 00 00 finger l3, field F armature A to ground G. The magnet-coils are cut out, as will be seen, and the purpose of this position is simply to overcome the inertia of the armatures and start their rotation before actuating the clutches. The position is not indicated to the operator, for the reason that there should be nothing to induce him to stop on this position. Passing to position No. 1 the path of the current is from T to finger 7, contacts 0 0 through one section of each magnet-coil in parallel, and then through the two motors in series, as before. In position No. 2 the only change made is that finger 8 loses engagement with contact a and finger 9 engages contact 0 This brings into circuit an additional section of each magnet-coil. In position No. 3 finger 9 has left the contact 0 and finger 10 has engaged contact 0 This puts the magnet-coils O (l entirely in circuit. Further movement of the switch opens the circuit through the magnet-coils and motors preparatory to passing to multiple. In passing to the first multiple position the fingers 7, 11, 12, 13, 1 1, and 15 first respectively engage the contacts y, M, 3 y, 11 and y, and the path of the current is from the trolley to finger 7, contacts y g fingers l1 and 12. Here the current divides, one part passing through field F, armature A, finger 14:, contacts .1 1 finger 15 to ground and theother part by contacts 1 y, finger 13, field F armature A to ground. This position is not indicated on the controller-index, as it is not desired to have the operator stop on this position. In positions 4, 5, and 6 contacts 0 c and c operate successively to gradually connect. in circuit the sections of the magnet-coils in precisely the same manner as the contacts 0 c c in positions 1, 2, and 3, and it will not be necessary to again trace out the circuit in detail. The current after passing through the magnet-coils or sections thereof passes through the two motors in parallel by the path traced out in position Y, except that contacts 0 c", 0 and 0 take the place of the contacts on the line Y. It will be seen, therefore, that I start the motors momentarily disconnected from the parts to be driven and gradually effeet a connection with such parts by gradu- Fally increasing the action of the magnetic clutch, the magnet-coils building up in strength as the current passing theret ugh I lrol .v e I IIO increases and as more sections a in circuit. I then open the circuitan-d pass to multiple, repeating th ew operation of gradually strengthening the'actigni of the. clutch. On downgrades theswitch can be thrown to off position, which not only opens the circuit through the motors," bnt also "through the magnet-coils, and thereby releases the clutches. This permits the motors to remain idle and saves the wear of gears at the commutators and bearings and also prevents accidents due to bursting of armatn refbands;

It will be readily seen that the greater the load and the larger the current taken by the motors the stronger becomesthe action of the clutch, its strength building up as the load increases; also,.that when the clutch is free from slippage the counterelectromotive force of the motors holds back the current, so that there is no useless Waste of current. The gradual manner in which the driving connection is made prevents lurching and jerking of the car-body in starting and 'rednces largely the strain and shock on the car-body and truck. It should be noted also thatinasmuch as no artificial resistance islen iployed to regulate the strength of the -cltgteli magnet-coils thedcurrent passing to the motors is not lim- 1 e I do not wish to limit myself in theemploy" ment of my improved method to the particular construction'of ciutch herein shown and described nor to the use of the particular switch shown, since I may'employ any suitable means for regulating the number of effecfive ampere-turns in the clutch magnetcm s.

The novel means herein described are not claimed herein, as they form the subject-matter of a pending application, Serial NC. 728,379, filed August 24,-"1899, of which th present application-is a division.

Having thus described my inven ion, wha. I claim, and desire to protect by Letters Patent, is-

- connected 1. The method of controlling aplurality of electric motors which consists in starting them connected in series and mechanically disconnected from the parts to be driven thereby, then eficctinga gradual mechanical conn ectionbetween the motors and the driven parts, then changing the motors over to parallel relation.

2. The method of controllingaplurality of electric motors, which consists in starting them connected in series and mechanically disconnected from the parts to be driven thereby, then efiecting a gradual mechanical connection between the motors and the driven parts, then opening the circuit through the motors and disconnecting them from the driven parts, then connecting them in mnltiplr with each other, and finally again gradually connecting them with the driven parts.

3. The method of controllinga plurality of electric motors, which consists in starting them from a position of rest connected in series with each other and mechanically disconiected from the mechanism to be driven thereby, then effecting electromagnetically a gradual mechanical connection between said motors and mechanism, and then shifting the motors over to parallel relation, substantially as described.

4. The method of controlling a plurality of electric motors, hich consists in starting them from a position-of rest mechanically disconnected from the mechanism to be driven thereby, then effecting gradually a mechanical driving connection between said motors and mechanism, and in conjunction therewith accelerating the speed of the motors by changing them from series to parallel relation, substantially as described.

In testimony whereof I have afiixed my signature in presence of two witnesses.

FRANK W. GARRETT.

Witnesses:

MYRTLE E. SHARPE, H. W. SMITH.- 

